1. Field of the Invention
The invention relates to a railway bogie designed for propulsion by a linear induction motor, to an arrangement for mounting a linear induction motor to a bogie of a railway vehicle, in particular an arrangement equipped with an adjustment device for adjusting the height of the linear induction motor relative to a reaction rail. It also relates to a method for mounting a linear induction motor to a bogie of a railway vehicle, and to a method for adjusting the distance between the linear motor and the reaction rail.
2. Description of the Related Art
Linear inductors consisting of field windings placed above one or several reaction rails and supplied with poly-phase current producing a moving field between the field windings on the vehicle and the running surface of the rails are used in railway vehicles for providing electromagnetic brakes and/or linear motor propulsion units. In all cases, correct and controllable operation of the electromagnetic brake or motor requires the preservation, during normal service, of a constant or nearly constant air gap between the field windings and the running surface of the reaction rail. This air gap is smaller for linear induction motors than for electromagnetic brakes, typically between 9 and 24 mm.
A resilient supporting device for a railway linear motor is disclosed in U.S. Pat. No. 3,516,364. The field windings are attached to a rigid frame connecting the four axle boxes of a conventional bogie. The rigid frame consists of two longitudinal members whose ends rest on the four axle boxes of the wheel axles, and two cross members. Two inductors are located on each side of the longitudinal vertical mid plane of the bogie. Each inductor is supported via a series of lateral resilient studs on the longitudinal members. Additional longitudinal resilient studs are used to transmit longitudinal traction forces to the cross-members. The longitudinal frame members are attached to the axle boxes via means comprising a screw and nut connection for adjusting the vertical position of the longitudinal member with respect to the axle boxes. However, precise adjustment of the position of the frame and inductors proves difficult, since each of the four screw and nut connections simultaneously influences the roll and pitch angles of the frame.
A steerable railway truck with a linear induction motor is known from U.S. Pat. No. 4,440,092. The truck is supported on four flanged wheels, whose wheel axles are rotationally retained in journal housings. The journal housings are secured to a front and a rear yoke, respectively. The truck is connected to the car body of the railway vehicle by means of a bolster and associated secondary suspension elements to support the car body. The front and rear yoke are articulated to the bolster to allow steering of the front and rear axles. The linear induction motor is supported relative to the yokes by means of a system of three vertical links, comprising one single link centrally positioned in the mid vertical longitudinal plane of the bogie to connect the linear motor unit to the outboard yoke and a pair of suspension links located on opposite sides and at equal distance of the mid vertical longitudinal plane of the bogie.
A bogie with a linear induction motor is known from EP 0 102 551. The bogie is provided with two wheel sets, each provided with a pair of axle boxes, a saddle casting fitted over each axle box to allow relative vertical motion between the axle box and the saddle, a bogie frame rigidly secured to the four saddle and a primary suspension between the interposed between the frame and the axle boxes. The axle on each wheel set is surrounded by a U-shaped beam supported at its ends on a pair of bearings located close to the wheels. Each beam is provided with one centrally located resilient universal joint for hanging one longitudinal end of an inductor of a linear induction motor. This arrangement does not provide any resilient suspension of the U-shape beams, and the bearings between the beams and the shaft experience high acceleration levels. The linear inductor motor is supported by two universal joints only and is free to roll about a longitudinal horizontal axis crossing the centres of the universal joints. This motion, however, is not acceptable when the air gap is small. Moreover, it is not possible to adjust the cross-level error of the linear inductor, i.e. the height difference between the left and right sides of the inductor, because the inductor is suspended from two points only spaced apart along the longitudinal centre axis of the vehicle.